1. Field of the Invention
The present invention relates to an auxiliary light source as an alternative to a discharge lamp when a lighting circuit for controlling discharge lamps for a vehicle malfunctions.
2. Background of the Invention
A known lighting circuit for a vehicular discharge lamp, such as a metal halide lamp, includes a DC power circuit, a DC-AC converting circuit and a starting circuit (or a starter circuit).
As a light source for a vehicle, a plurality of discharge lamps needs to be controlled. If the lighting circuit is provided for each discharge lamp, cost and space may pose a problem. Therefore, a circuit is designed such that the discharge lamps are turned on by using a common lighting circuit. For example, as a light source for an automobile, the headlamps are provided on the right and left, front sides of the vehicle. As a result, at least two discharge lamps are required and a common lighting circuit is required for both discharge lamps. Moreover, to have a high beam (main beam) and a low beam (dipped beam) generated by separate discharge lamps (a four-lamp type illumination), a pair of discharge lamps would be required on the right and the left sides and a lighting circuit common to both of them would be necessary.
However, if the lighting circuit provided in common to the discharge lamps malfunctions, at worst, all the discharge lamps might go out. Therefore, the worst case scenario may pose a great problem in night driving.
Therefore, an object of the invention is to ensure sufficient illumination by an auxiliary light source in case the lighting circuit fails to turn the discharge lamps on.
An implementation of the invention provides a lighting system for a vehicle comprising a plurality of discharge lamps and a lighting circuit capable of controlling lighting operations of the discharge lamps at the same time, and an auxiliary lighting circuit for turning on an auxiliary light source in place of the discharge lamp when an abnormality in the lighting circuit is detected.
According to an implementation of the invention, therefore, if the abnormality in the lighting circuit of the discharge lamp is detected, the illumination necessary for driving can be obtained by turning the auxiliary light source on.